Prevalence of and risk factors for low bone mineral density in untreated HIV infection: A substudy of the INSIGHT Strategic Timing of AntiRetroviral Treatment (START) trial

Objectives: HIV infection is associated with a higher prevalence of low bone mineral density (BMD) and fractures than that found in the general population. There are limited data in HIV-positive adults, naïve to antiretroviral therapy (ART), with which to estimate the relative contribution of untreated HIV infection to bone loss. Methods: The primary objective of the Strategic Timing of AntiRetroviral Treatment (START) Bone Mineral Density Substudy is to compare the effect of immediate versus deferred initial ART on bone. We evaluated traditional, demographic, HIV-related and immunological factors for their associations with baseline hip and lumbar spine BMD, measured by dual-energy X-ray absorptiometry, using multiple regression. Results: A total of 424 ART-naïve participants were enrolled at 33 sites on six continents; the mean age was 34 years [standard deviation (SD) 10.1 years], 79.0% were nonwhite, 26.0% were women, and 12.5% had a body mass index (BMI)<20kg/m2. Mean (SD) Z-scores were -0.41 (0.94) at the spine and -0.36 (0.88) for total hip; 1.9% had osteoporosis and 35.1% had low BMD (hip or spine T-score<-1.0). Factors independently associated with lower BMD at the hip and spine were female sex, Latino/Hispanic ethnicity, lower BMI and higher estimated glomerular filtration rate. Longer time since HIV diagnosis was associated with lower hip BMD. Current or nadir CD4 cell count and HIV viral load were not associated with BMD. Conclusions: In this geographically and racially diverse population of ART-naïve adults with normal CD4 cell counts, low BMD was common, but osteoporosis was rare. Lower BMD was significantly associated with traditional risk factors but not with CD4 cell count or viral load.